After the Boston Red Sox secured an American League Championship Series berth with a nail-biting win over the Yankees in Game 4 of the ALDS on Tuesday, they returned to Boston to prepare for a best-of-seven set with a Houston Astros club that swept the Cleveland Indians in their first-round matchup.

The Red Sox finished the regular season with an MLB-best 108-54 record, but they face a tough draw in the 2018 ALCS against an Astros club that went 103-59 – the league’s second-best mark – after winning the World Series in 2017.

27 outs

Though these same clubs met in the ALDS just last year and the Astros took a convincing victory, the 2018 version of their matchup looks to be a fairer fight after the Red Sox blitzed through the regular season and beat up on the 100-win Yankees in the divisional series.

For Boston, the series represents its first time reaching the LCS since a championship run in 2013. Amazingly, the only holdovers from the 2013 postseason roster likely to appear in the ALCS are shortstop Xander Bogaerts and reliever Brandon Workman.

The Sox were able to finish off the Yankees in four games in their ALDS, sparing ace Chris Sale the need for a Game 5 start that would’ve held him out of the first game in this series. The lanky lefty appeared in relief on his throw day on Tuesday, dominating Yankees hitters in a scoreless eighth. He’ll square off with Justin Verlander on Saturday in a matchup of two of the league's most bankable aces, and two pitchers who looked like the likely top finishers for the AL Cy Young Award at midseason – before Sale spent most of August on the disabled list and Rays lefty Blake Snell pitched his way into the conversation.

The Astros are looking to defend their 2017 title with a similar cast of characters, plus the notable addition of Game 2 starter Gerrit Cole. This year’s Astros showed no signs whatsoever of any World Series hangover, winning 20 of their first 30 games in the regular season. They hit a cold stretch around the All-Star break, but went 21-6 in September to outlast the Athletics and Mariners in a surprisingly competitive division.

Houston made quick work of the Cleveland Indians in the ALDS, sweeping the series and outscoring their opponents by a 15 runs across the three games. Astros hitters batted .327 with a 1.037 OPS in the series while their pitchers finished it with a 2.00 ERA and a 0.70 WHIP.

Keep an eye on...

Astros shortstop Carlos Correa. The young star shined as brightly as ever in the 2017 postseason, but struggled with back issues during the regular season and spent all of August on the disabled list in a disappointing campaign that saw him finish with career worsts in practically all offensive categories.

He hit only .180 with a .517 OPS in 37 regular-season games after returning from the DL, and notched only one hit – his Game 3 home run – in 10 at-bats in the ALDS. Correa said this week that he still feels intense pain in the area, especially when he swings and misses. He intends to continue playing through the injury, and the Astros’ division-series sweep provided him four full days off to rest before the ALCS.

Houston’s remarkable flexibility means it is perhaps better suited than any other club to withstand the potential loss of a player like Correa – both Alex Bregman and Marwin Gonzalez filled in for Correa during his absence. But the diminished version of Correa marks a potential hole in Houston’s otherwise stacked batting order.

Close and late

The Red Sox’ ALDS win trivialized some concerns in the bullpen that arose during the series. Most concerningly, closer Craig Kimbrel – normally their lone dominant option for the late innings – allowed a home run to Aaron Judge in his Game 1 appearance then nearly blew a three-run lead in Game 4. Kimbrel struggled to throw strikes in his Tuesday appearance, and needed some help from overeager Yankees hitters to escape the ninth inning. Of the Sox’ various underwhelming options for the middle innings, Ryan Brasier was best during the regular season. The 31-year-old Brasier pitched in Japan in 2017, but signed with the Red Sox in March and yielded a 1.60 ERA in 34 regular-season appearances after joining the big-league club in July.

The Astros feature a very different bullpen mix than they did last October, with volatile closer Ken Giles sent to Toronto in a deadline deal for Roberto Osuna while the latter was still serving a 75-game suspension for violating the league’s domestic violence policy. Osuna and fellow July acquisition Ryan Pressly both performed extremely well for Houston down the stretch, strengthening a late-inning mix that already included converted starter Collin McHugh. The depth in the Astros’ starting rotation should continue to help their postseason bullpen, both because their starters tend to work deep into games and because those squeezed out of a playoff rotation – namely Lance McCullers – make for great relief options.

In the end

It’s hard to bet against a team that won 108 games in one of the league’s most competitive divisions in the regular season, but the Red Sox enter the ALCS with too much uncertainty in their pitching staff for comfort. David Price’s postseason struggles have been well documented, though manager Alex Cora says the Sox identified and corrected some unspecified issue that hampered since late in the regular season. After Kimbrel’s bout of Game 4 wildness, the Sox’ bullpen looks beatable.

The Red Sox have baseball’s best offense, but the Astros’ strong starting rotation should mitigate the damage done by the likes of Mookie Betts and J.D. Martinez. Houston has no apparent weaknesses whatsoever, and enough depth on their roster to mitigate any that may arise.

Prediction: Astros in 6

Related slideshow: Best of the 2018 MLB playoffs (Provided by photo services)